lean Ethereum Part 2: PQ Signatures and Poseidon with Dmitry and Benedikt

youtube.com/watch?v=xh8hbz1nqxQ

In this episode, Nico Mohnblatt (x.com/nico_mnbl) speaks with Benedikt Wagner (benedikt-wagner.dev) and Dmitry Khovratovich (x.com/Khovr), cryptography researchers at the Ethereum Foundation (ethereum.foundation), for the second instalment of the lean Ethereum miniseries. They explore leanSig, a hash-based multi-signature scheme designed as a post-quantum replacement for BLS in Ethereum consensus.

The conversation walks through how one-time signatures and Merkle trees can be combined to support long-lived validators, and why SNARK-based aggregation is needed in a post-quantum setting. The talk touches on key tradeoffs like signature size versus verification speed, encoding challenges behind their At the Top of the Hypercube (eprint.iacr.org/2025/889.pdf) work, and the role of Poseidon as the core hash function.
Related Links

• lean Ethereum Part 1: Introduction with Justin Drake (zeroknowledge.fm/podcast/391)
• lean Ethereum (blog.ethereum.org/2025/07/31/lean-ethereum)
• Lean Consensus R&D Progress (leanroadmap.org)
• leanSig Implementation (github.com/leanEthereum/leanSig)
• Poseidon2: A Faster Version of the Poseidon Hash Function (eprint.iacr.org/2023/323.pdf)
• At the Top of the Hypercube – Better Size-Time Tradeoffs for Hash-Based Signatures (eprint.iacr.org/2025/889.pdf)
• Hash-Based Multi-Signatures for Post-Quantum Ethereum (eprint.iacr.org/2025/055)
• Technical Note: LeanSig for Post-Quantum Ethereum (eprint.iacr.org/2025/1332.pdf)
• Aborting Random Oracles: How to Build them, How to Use them (eprint.iacr.org/2026/016.pdf)
• The Billion Dollar Merkle Tree (eprint.iacr.org/2026/089.pdf)
• Poseidon: A New Hash Function for Zero-Knowledge Proof Systems (usenix.org/conference/usenixsecurity21/present…)
• Poseidon Cryptanalysis Initiative (poseidon-initiative.info)

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Read transcript (github.com/ZeroKnowledgefm/episode-transcripts…)